Modular assembly for aftertreatment system

ABSTRACT

A modular assembly for an exhaust aftertreatment system is provided. The modular assembly includes an inlet portion. The modular assembly also includes a mixing element. The modular assembly further includes a first frusto-conical region diverging from the inlet portion. The modular assembly also includes a selective catalytic reduction assembly provided within a central portion of the housing. The selective catalytic reduction assembly includes a bank of catalysts. The modular assembly further includes a sound suppression element provided within the central portion of the housing and positioned downstream of the selective catalytic reduction assembly. The modular assembly includes a baffle arrangement provided within the central portion of the housing, the baffle arrangement includes a first baffle and a second baffle. The modular assembly also includes a second frusto-conical region converging from the central portion of the housing. The modular assembly further includes an outlet portion connected to the second frusto-conical region.

Technical Field

The present disclosure relates to a modular assembly, and moreparticularly to the modular assembly for an aftertreatment systemassociated with an engine.

BACKGROUND

An aftertreatment system is associated with an engine system. Theaftertreatment system is configured to treat and reduce oxides ofnitrogen (NOx) present in an exhaust gas flow, prior to the exhaust gasflow exiting into the atmosphere. In order to reduce NOx, theaftertreatment system may include a reductant delivery module, areductant injector, and a Selective Catalytic Reduction (SCR) module.

The aftertreatment system may additionally include a muffler assemblyhaving a sound suppression element. The sound suppression elementperforms sound attenuation function and suppresses noise of highpressure created by the exhaust gas. Generally, the muffler assembly isprovided as a separate module downstream of the SCR module. In someexamples, the SCR module and the sound suppression element areintegrated into a single muffler assembly. However, the SCR moduleincludes square cross-sectioned SCR units. Such shape of the SCR unitsmay lead to an increase in stresses caused due to pressure pulsations.Further, stresses are also induced across weld joints thereby affectinga mounting of the SCR units within the muffler assembly. In somesituations, such a design of the SCR units causes increase in hoopstresses.

U.S. Pat. No. 5,578,277 hereinafter referred to as '277 patent,describes a modular catalytic converter and muffler used to purifyexhaust from a relatively large diesel engine. The modular catalyticconverter and muffler includes a plurality of catalytic convertersub-cans mounted within a housing of the modular catalytic converter andmuffler. The modular catalytic converter and muffler also includes aflow distributor mounted within the housing upstream of the catalyticconverter sub-cans. Further, a muffler structure is mounted within thehousing between the catalytic converter sub-cans and an outlet in orderto attenuate noise in the exhaust. However, the modular catalyticconverter and muffler of the '277 patent has a bulky structure.

SUMMARY OF THE DISCLOSURE

In one aspect of the present disclosure, a modular assembly for anexhaust aftertreatment system is provided. The modular assembly includesan inlet portion defined by a housing of the modular assembly. The inletportion is configured to connect to an exhaust conduit. The modularassembly also includes a mixing element positioned within the inletportion and downstream of a reductant injector with respect to anexhaust gas flow direction. The modular assembly further includes afirst frusto-conical region diverging from the inlet portion. Themodular assembly also includes a selective catalytic reduction assemblyprovided within a central portion of the housing. The selectivecatalytic reduction assembly includes a bank of catalysts positioned ina vertical arrangement with respect to each other. A central axis ofeach of the bank of catalysts is parallel to a central axis of theexhaust conduit. The modular assembly further includes a soundsuppression element provided within the central portion of the housingand positioned downstream of the selective catalytic reduction assembly.The modular assembly includes a baffle arrangement provided within thecentral portion of the housing. The baffle arrangement includes a firstbaffle provided upstream of the selective catalytic reduction assemblyand a second baffle provided downstream of the sound suppressionelement. Further, the central portion of the housing containing thebaffle arrangement, the selective catalytic reduction assembly, and thesound suppression element has an oblong cross section. The modularassembly also includes a second frusto-conical region converging fromthe central portion of the housing. The modular assembly furtherincludes an outlet portion connected to the second frusto-conicalregion.

Other features and aspects of this disclosure will be apparent from thefollowing description and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of an exemplary engine system having anaftertreatment system associated therewith, according to one embodimentof the present disclosure;

FIG. 2 is a partial cut-away view of an exemplary modular assemblyassociated with the aftertreatment system, according to one embodimentof the present disclosure; and

FIG. 3 is a partial perspective view shown without the top cover of themodular assembly of FIG. 2.

DETAILED DESCRIPTION

Wherever possible, the same reference numbers will be used throughoutthe drawings to refer to the same or the like parts. Referring to FIG.1, a schematic diagram of an exemplary engine system 100 is illustrated,according to one embodiment of the present disclosure. The engine system100 includes an engine 102, which may be an internal combustion engine,such as, a reciprocating piston engine or a gas turbine engine. Theengine 102 is a spark ignition engine or a compression ignition engine,such as, a diesel engine, a homogeneous charge compression ignitionengine, or a reactivity controlled compression ignition engine, or othercompression ignition engines known in the art. The engine 102 may befueled by gasoline, diesel fuel, biodiesel, dimethyl ether, alcohol,natural gas, propane, hydrogen, combinations thereof, or any othercombustion fuel known in the art.

The engine 102 may include other components (not shown), such as, a fuelsystem, an intake system, a drivetrain including a transmission system,and so on. The engine 102 may be used to provide power to a machine (notshown) including, but not limited to, an on-highway truck, anoff-highway truck, an earth moving machine, an electric generator, andso on. Accordingly, the engine system 100 may be associated with anindustry including, but not limited to, transportation, construction,agriculture, forestry, power generation, and material handling.

The engine system 100 includes an exhaust aftertreatment system 104,hereinafter interchangeably referred to as the aftertreatment system 104fluidly connected to an exhaust manifold (not shown) of the engine 102.The aftertreatment system 104 may treat an exhaust gas flow exiting theexhaust manifold of the engine 102. The exhaust gas flow containsemission compounds that may include oxides of nitrogen (NOx), unburnedhydrocarbons, particulate matter, and/or other combustion products knownin the art. The aftertreatment system 104 may trap or convert NOx,unburned hydrocarbons, particulate matter, combinations thereof, orother combustion products present in the exhaust gas flow, beforeexiting the engine system 100.

The aftertreatment system 104 includes a modular assembly 200. Themodular assembly 200 is provided in fluid communication with an exhaustconduit 106. Referring to FIG. 2, the modular assembly 200 includes ahousing 202. The housing 202 may be made from any metal or polymer knownin the art. Further, parameters related to the housing 202 such as size,shape, location, and material used may vary according to system designand requirements, without limiting the scope of the present disclosure.

The housing 202 of the modular assembly 200 defines an inlet portion204. The inlet portion 204 may include a circular cross section.Alternatively, the inlet portion 204 may include an oblong, square, orrectangular cross section. The inlet portion 204 of the housing 202receives the exhaust gas flow from the exhaust manifold via the exhaustconduit 106 (see FIG. 1). A first end of the inlet portion 204 isconfigured to connect to the exhaust conduit 106.

Referring now to FIG. 1, the aftertreatment system 104 may include areductant supply system 108 associated therewith. A reductant isinjected into the inlet portion 204 (see FIG. 2) by a reductant injector110 associated with the reductant supply system 108. The reductant maybe a fluid, such as, Diesel Exhaust Fluid (DEF). The reductant mayinclude urea, ammonia, or other reducing agent known in the art.

The reductant supply system 108 includes a reductant tank 112. Thereductant is contained within the reductant tank 112. Parameters relatedto the reductant tank 112 such as size, shape, location, and materialused may vary according to system design and requirements. Further, thereductant injector 110 may be communicably coupled to a controller (notshown). Based on control signals received from the controller, thereductant from the reductant tank 112 is provided to the reductantinjector 110 by a pump assembly 114. The amount of the reductant thatmay be injected into the inlet portion 204 may be appropriately meteredbased on engine operating conditions. In one example, a NOx sensor (notshown) may be mounted in the inlet portion 204. The NOx sensor maymeasure an amount of NOx present in the exhaust gases entering the inletportion 204. The NOx sensor may send a signal indicative of the NOx inthe exhaust gases to the controller or an ECM (not shown) present onboard the machine. The NOx sensor 260 may include any known sensorcapable of measuring NOx present in the exhaust gases, without limitingthe scope of the present disclosure.

Referring to FIG. 2, as the reductant is injected into the inlet portion204, the reductant mixes with the exhaust gas flow passing therethrough,and is carried towards a mixing element 208 positioned within the inletportion 204. The mixing element 208 is positioned downstream of thereductant injector 110 with respect to an exhaust gas flow direction“F”. The mixing element 208 may embody a swirl mixer or a flapper mixer.Alternatively, any known mixing element 208 may be used without limitingthe scope of the present disclosure. The mixing element 208 allowsuniform mixing of the exhaust gas flow and the reductant injected intothe inlet portion 204. Further, mixing vanes or turbulators may also beassociated with the modular assembly 200 to provide turbulence in theexhaust gas flow.

The inlet portion 204 is connected to a first frusto-conical region 216.The first frusto-conical region 216 diverges from the inlet portion 204.More particularly, the first frusto-conical region 216 includes adiverging profile along the exhaust gas flow direction “F”. In someexamples, a surface 218 of the first frusto-conical region 216 may makean angle of approximately 45° with an axis X-X′ (see FIG. 1) of theexhaust conduit 106 of the modular assembly 200. The firstfrusto-conical region 216 deflects a portion of the exhaust gas flowreceived from the inlet portion 204.

The housing 202 includes a central portion 220. The central portion 220is provided downstream of the first frusto-conical region 216 withrespect to the exhaust gas flow direction “F”. The central portion 220has an oblong cross section, having a pair of curved sections at a topportion and a bottom portion respectively. The curved sections of thecentral portion 220 respectively define an upper interior wall 222 and alower interior wall 224.

Referring to FIGS. 2 and 3, a baffle arrangement 226 is provided withinthe housing 202 and downstream of the first frusto-conical region 216with respect to the exhaust gas flow direction “F”. The bafflearrangement 226 may perform a flow distribution function in order toevenly or uniformly distribute the exhaust gas flow receivedtherethrough. The baffle arrangement 226 is provided and coupled to thecentral portion 220 of the housing 202. The baffle arrangement 226includes a first baffle 228 provided upstream of a selective catalyticreduction (SCR) assembly 246 with respect to the exhaust gas flowdirection “F”. The baffle arrangement 226 also includes a second baffle230. The second baffle 230 is provided downstream of a sound suppressionelement 252 with respect to the exhaust gas flow direction “F”. Thefirst and second baffles 228, 230 are provided perpendicular to theexhaust gas flow direction “F”.

The first and second baffles 228, 230 have a similar design. The designof the first baffle 228 will now be explained in detail. Referring toFIG. 3, a tilted cutaway perspective view of the modular assembly 200 isillustrated. As shown, the first baffle 228 includes an oblong shapecorresponding to the shape of the central portion 220 of the housing202. The first baffle 228 includes a pair of curved profiles near a topend and a bottom end.

A face 236 of the first baffle 228 is defined between the curvedprofiles of the first baffle 228. The face 236 of the first baffle 228includes a planar profile. The face 236 of the first baffle 228 includesa number of central bores 238. In one embodiment, the first baffle 228includes three central bores 238. Further, a number of openings 240 areprovided on the face 236 such that the openings 240 surround each of thecentral bore 238. In one example, six openings 240 may be provided onthe face 236 of the first baffle 228. However, the number of openings240 may vary as per system requirements. The central bore 238 and theopenings 240 allow uniform mixing and distribution of the exhaust gasflow with the reductant.

Referring to FIG. 2, the first and second baffles 228, 230 include legportions 242, 244. The leg portions 242, 244 extend along the axis X-X′from the first and second baffles 228, 230. Each of the leg portions242, 244 connects the first and second baffles 228, 230 to therespective walls 222, 224 of the central portion 220 of the housing 202.The first and second baffles 228, 230 are welded to the central portion220. In one example, an overlapping weld or a fillet weld is used toweld the first and second baffle 228, 230 to the central portion 220.The welding is done in a manner that minimizes stress induced on accountof pressure pulsations. Alternatively, any other fastening means mayalso be used to connect the first and second baffles 228, 230 to thecentral portion 220 of the housing 202.

As shown in FIGS. 2 and 3, the modular assembly 200 includes the SCRassembly 246 provided within the central portion 220 of the housing 202.The SCR assembly 246 operates to treat exhaust gases exiting the engine102 in the presence of ammonia, which is provided after degradation ofthe reductant injected into the exhaust gas flow in the inlet portion204. The SCR assembly 246 is provided downstream of the first baffle 228along the exhaust gas flow direction “F”. The SCR assembly 246 includesan oblong shape corresponding to the shape of the central portion 220.This shape of the SCR assembly 246 allows for a reduction in stressescaused due to pressure pulsations.

The SCR assembly 246 includes a bank of catalysts 248 positioned in avertical arrangement with respect to each other, such that a centralaxis Y-Y′ (see FIG. 2) of each of the bank of catalysts 248 is parallelto the axis X-X′ (see FIG. 1) of the exhaust conduit 106. In oneexample, three catalysts 248 may be associated with the SCR assembly246. Alternatively, the number of catalysts 248 may vary based on systemrequirements. The catalysts 248 may include a circular, oval,elliptical, oblong, or any other cross section, without limiting thescope of the present disclosure. It should be noted that the SCRassembly 246 is removably mounted within the housing 202. Further, thecatalysts 248 may also be removed or replaced as per requirements. TheSCR assembly 246 may include holding plates (not shown) to removablycouple the SCR assembly 246 within the housing 202. It should be notedthat the first and second baffles 228, 230 are arranged such that thefirst and second baffles 228, 230 distribute the exhaust gases uniformlyacross the catalysts 248.

The modular assembly 200 includes the sound suppression element 252provided within the housing 202. The sound suppression element 252 ispositioned downstream of the SCR assembly 246 with respect to theexhaust gas flow direction “F”. The sound suppression element 252 isembodied as an acoustic sound-proofing element that performs soundattenuation or noise absorbing function. More particularly, the soundsuppression element 252 reduces the amount of noise of sound pressurecreated by the exhaust gas flow exiting the engine 102.

The sound suppression element 252 includes a mesh like structure and maybe made of any known sound absorbing material known in the art thatexhibits high heat resistance and high noise absorbing efficiency. Inone example, the sound suppression element 252 may include a latticestructure, and may be made of steel wool, mineral wool, glass wool, orany permeable membrane like structure. The sound suppression element 252may include an oblong cross section corresponding to the cross sectionof the central portion 220. Further, the sound suppression element 252may have variable width. More particularly, the width of the soundsuppression element 252 may be varied as per the sound attenuationrequirements.

The modular assembly 200 also includes a second frusto-conical region254. The second frusto-conical region 254 converges from the centralportion 220 of the housing 202. The second frusto-conical region 254 ispositioned downstream of the sound suppression element 252 with respectto the exhaust gas flow direction “F’. The second frusto-conical region254 may deflect and direct the exhaust gases towards an outlet portion256. The outlet portion 256 is connected to, and provided downstream ofthe second frusto-conical region 254 with respect to the exhaust gasflow direction “F”. In some examples, a surface 258 of the secondfrusto-conical region 254 may make an angle of approximately 45° withthe axis X-X′. In one example, the outlet portion 256 may be providedinline with the inlet portion 204 to reduce back-pressure within themodular assembly 200.

A NOx sensor 260 may be mounted in the outlet portion 256. The NOxsensor 260 may measure an amount of NOx present in the exhaust gasesflowing through the outlet portion 256. The NOx sensor 260 may send asignal indicative of the NOx in the exhaust gases to the controller oran ECM (not shown) present on board the machine. The NOx sensor 260 mayinclude any known sensor capable of measuring NOx present in the exhaustgases, without limiting the scope of the present disclosure.

The exhaust gas flow enters the inlet portion 204 of the modularassembly 200 from the exhaust conduit 106. As the exhaust gases flowthrough the inlet portion 204, the reductant is injected therein. As theexhaust gas flows through the inlet portion 204, the mixing element 208enhances mixing of the reductant with the exhaust gas flow entering intothe first frusto-conical region 216. The exhaust gases are thendeflected by the first frusto-conical region 216, and flow through eachof the baffles 228, 230, the SCR assembly 246, and the sound suppressionelement 252. The treated exhaust gases are then deflected from theirpath towards the outlet portion 256. In one embodiment, the exhaustgases are let out into the atmosphere from the outlet portion 256.

The housing 202 of the modular assembly 200 may be cast as a unitarycomponent. Alternatively, the components of the housing 202 such as theinlet portion 204, the first frusto-conical region 216, the centralportion 220, the second frusto-conical region 254, and the outletportion 256 may be manufactured as separate units and assembled later onto form the housing 202. The components of the housing 202 may beconnected to each other using any conventional joining process known inthe art. In some situations, welding may be used to join the componentsof the housing 202. For example, overlapped welded joints may be used tojoin the components together. Further, the modular assembly 200 may besupported and secured to the machine externally via a band type or straptype wrap-around clamp (not shown) that allow unconstrained thermalexpansion of the modular assembly 200 during operation.

The aftertreatment system 104 disclosed herein is provided as anon-limiting example. It will be appreciated that the aftertreatmentsystem 104 may be disposed in various arrangements and/or combinationsrelative to the exhaust manifold. These and other variations inaftertreatment system design are possible without deviating from thescope of the disclosure. For example, the aftertreatment system 104 mayinclude components (not shown), such as, a Diesel Oxidation Catalyst(DOC) unit, a Diesel Particulate Filter (DPF) unit, and/or an AmmoniaOxidation Catalyst (AMOX) without limiting the scope of the disclosure.

INDUSTRIAL APPLICABILITY

The present disclosure describes providing the sound suppression element252 and the SCR assembly 246 within the single modular assembly 200. Thehousing 202 of the modular assembly 200 has an oblong shape withoverlapped welded joints. As the housing 202 has a compact shape, themodular assembly 200 can be accommodated and mounted in a compactmounting space. This design of the housing 202 leads to the reduction instresses induced due to pressure pulsations. The design of the housing202 further allows for a smooth flow of the exhaust gases within thehousing 202. The modular assembly 200 includes the baffle arrangement226 provided upstream of the SCR assembly 246 with respect to theexhaust gas flow direction “F”. The baffle arrangement 226 functions touniformly distribute the exhaust gas flow across a face of the SCRassembly 246. The first and second baffles 228, 230 are mounteddiametrically opposite to each other within the housing 202 usingoverlapping weld or fillet weld. Such welding joints help in thereduction in pressure pulsations and stresses induced by the pressurepulsations.

The SCR assembly 246 includes a curved profile, as against conventionalsquare profile. This leads to reduction in the stresses caused due topressure pulsations. Hence, hoop or circumferential stresses induced inthe SCR assemblies of earlier designs may be avoided. The SCR assembly246 includes the catalysts 248. The catalysts 248 are removably providedwithin the housing 202, such that they may be conveniently removed forservicing or replacement as per system requirements. Further, thecomplete SCR assembly 246 is removably mounted within the housing 202 bythe holding plates.

The modular assembly 200 may be supported and secured to the machineexternally via band/strap type wrap-around clamps. This type of mountingarrangement allow unconstrained thermal expansion of the modularassembly 200 during operation, thereby reducing stresses in the modularassembly 200 and its mounting materials. Also, the modular assembly 200of the present disclosure helps in reducing backpressure developed inthe system. In some examples, the back pressure in the system may reducefrom an existing 12 kPa to 4-6 kPa. The modular assembly 200 includesfewer components and is less bulky.

While aspects of the present disclosure have been particularly shown anddescribed with reference to the embodiments above, it will be understoodby those skilled in the art that various additional embodiments may becontemplated by the modification of the disclosed machines, systems andmethods without departing from the spirit and scope of what isdisclosed. Such embodiments should be understood to fall within thescope of the present disclosure as determined based upon the claims andany equivalents thereof.

What is claimed is:
 1. A modular assembly for an exhaust aftertreatmentsystem, the modular assembly comprising: an inlet portion defined by ahousing of the modular assembly, the inlet portion configured to connectto an exhaust conduit; a mixing element positioned within the inletportion and downstream of a reductant injector with respect to anexhaust gas flow direction; a first frusto-conical region diverging fromthe inlet portion; a selective catalytic reduction assembly providedwithin a central portion of the housing, the selective catalyticreduction assembly including a bank of catalysts positioned in avertical arrangement with respect to each other; such that a centralaxis of each of the bank of catalysts is parallel to a central axis ofthe exhaust conduit; a sound suppression element provided within thecentral portion of the housing and positioned downstream of theselective catalytic reduction assembly; and a baffle arrangementprovided within the central portion of the housing, the bafflearrangement including a first baffle provided upstream of the selectivecatalytic reduction assembly and a second baffle provided downstream ofthe sound suppression element, wherein the central portion of thehousing containing the baffle arrangement, the selective catalyticreduction assembly, and the sound suppression element has an oblongcross section; a second frusto-conical region converging from thecentral portion of the housing; and an outlet portion connected to thesecond frusto-conical region.